Type Of Buckling-restrained Brace Research Articles

Experimental and numerical study of the seismic performance of an all-steel assembled Q195 low-yield buckling-restrained brace

A new type of buckling-restrained brace (BRB), namely, an all-steel assembled Q195 low-yield-point buckling-restrained brace (LYBRB), is proposed in this paper. The difference between the LYBRB and a traditional BRB is that Q195 low-yield point steel with an in-line cross-section (which can better absorb seismic energy) of the core material is adopted. A Q235 steel core is used for the comparative analysis. Additionally, to prevent residual stress, water cutting is performed to cut the core plate. A quasi-static low-cycle reciprocating load test is conducted to determine its failure mode, hysteretic response and restoring force model. The seismic behavior of the LYBRB is evaluated according to the following performance indices: the hysteresis curve, skeleton curve, tension and compression nonuniform coefficient, energy dissipation coefficient, equivalent viscous damping ratio, plastic deformation performance, and in-plane and out-of-plane lateral displacements of the external restraining plate of the LYBRB. The failure mode of the LYBRB is tension-controlled; its hysteresis curve shows good symmetry, stability and fullness; and its energy dissipation capacity support is better. Combined with the restoring force model obtained via an experiment, the bilinear kinematic hardening model is adopted to conduct finite element (FE) numerical simulation analysis of the core plate. Comparison with the test results shows that both the failure mode and the hysteretic response are in good agreement. The influence factors (such as the gap-thickness ratio between the core plate and external restraining plate, width-thickness ratio, core material properties and slenderness ratio of the core plate in the weak-axis direction for the LYBRB) are then used to carry out a parametric analysis to provide better insight into the LYBRB.

Testing of Buckling-Restrained Braces with Replaceable Steel Angle Fuses

AbstractThis research focuses on a new type of buckling-restrained brace (BRB) with replaceable steel angle fuses. The proposed BRB offers ease of postearthquake examination of fuse damage, conveni...

Buckling-restrained brace with CFRP encasing: Mechanical behavior & cyclic response

Buckling-restrained braces (BRBs) have received considerable attention in seismic design of various types of structures. Conventional BRBs are composed of steel core and surrounding steel tube filled with concrete. Eliminating the steel tube can be advantageous to BRB. In this study the idea of replacing the steel tube by CFRP layers in BRBs is proposed. The advantages of this type of BRB are mentioned, and its design criteria are introduced. The construction procedure of two BRB specimens is described. The specimens are uniaxially tested based on moderate, and severe earthquake levels and the performance of the specimens is investigated. The backbone curves resulted from the hysteresis curve are presented for the design proposes. The results of this study show that CFRP layers can effectively provide the expected performance of the encasing, and the proposed BRB can be considered a viable alternative to the conventional BRBs.

A new shuttle-shaped buckling-restrained brace. Theoretical study on buckling behavior and load resistance

This paper proposes a new type of buckling-restrained braces (BRBs), namely shuttle-shaped buckling-restrained braces (SS-BRBs). The proposed SS-BRB is composed of a circular steel tube as the inner core, and a shuttle-shaped thin-walled steel tube as the external restraining member. The space between them is filled by a steel-plate isolation system. The shuttle-shaped restraining member of the SS-BRB significantly improves load-carrying efficiency and saves material in its strength design. Moreover, the SS-BRB is more aesthetically appealing and can be utilized as an exposed BRB in long-span or spatial structures. In terms of the concept of restraining ratio of a BRB, no design method of an SS-BRB is available currently because it concerns the solution of the elastic buckling load of an SS-BRB. Therefore, the elastic buckling load of a pin-ended SS-BRB is initially studied by adopting the equilibrium method and is further verified through finite element (FE) method. The lateral displacement function of an SS-BRB, and the longitudinal stress at the extreme fiber of the external restraining member are derived by considering an initial geometric imperfection that is consistent with the first order overall buckling shape of the SS-BRB. A correction factor considering shear deformation has been incorporated for a more accurate prediction. The lower limit of the restraining ratio for a load-bearing type of SS-BRBs is further obtained based on yielding of the extreme fiber of the restraining member. Furthermore, the proposed formula has incorporated a strain hardening factor for the SS-BRB that experiences strain hardening of the core after its initial yielding. The proposed formulas have been validated through FE numerical analysis. The findings in this paper provide fundamentals to develop the design method for an energy-dissipation type of SS-BRBs.

Theoretical and experimental investigation of core-separated buckling-restrained braces

Buckling behavior and hysteretic performance of a new type of buckling-restrained brace (BRB), namely core-separated buckling-restrained brace (CSBRB), are theoretically and experimentally investigated. The material utilization efficiency of the CSBRB is significantly improved compared with common BRB, since its cross-section spreads outwards by spacing two cores, thus improving the flexural rigidity of the restraining system. On the basis of the elastic buckling loads of pin-ended CSBRBs, a design procedure involving two design parameters, namely normalized slenderness and buckling factor, is firstly established. Then, hysteretic behavior of CSBRBs is investigated by FE nonlinear analysis to obtain the critical normalized slenderness. Finally, test results of four specimens with different normalized slenderness values are presented to reveal the hysteretic characteristics and the energy-dissipation abilities, concluding that a CSBRB with adequate restraining rigidity can provide stable hysteretic performance. The test results coincide well with the results obtained from refined FE numerical analyses.

Numerical and experimental studies of corrugated-web-connected buckling-restrained braces

This paper proposes a new type of buckling-restrained brace (BRB), the so-called corrugated-web connected buckling-restrained brace (CWC-BRB), which is a core-separated BRB. The external restraining system of the CWC-BRB is composed of two all-steel external tubes connected by either single or double sinusoidal corrugated webs. Each of the two cores of the CWC-BRB has a single steel plate section and an extended projection at each end of the CWC-BRB, and the two core projections at each end are connected by a core stiffener. The external restraining systems, corrugated webs, two cores and core stiffeners form a firm and robust I-section CWC-BRB, and the flexural stiffness and load-carrying capacity of the proposed steel CWC-BRB are much larger than those of ordinary single-cored steel BRBs. The elastic buckling load of the CWC-BRB is derived by considering the shear deformation of the corrugated webs in the external restraining system. The ultimate load-carrying capacity under monotonic axial compression of CWC-BRBs and their hysteretic and low-cycle fatigue performance under repeated compressive-tensile cyclic loads are investigated using a shell element FE model. In addition, the effect of the restraining ratio or normalized slenderness ratio on the load resistance and failure mode of a CWC-BRB is explored. To further investigate the hysteretic performance and corresponding failure modes of CWC-BRBs and to validate the FE model, experimental studies are reported on four CWC-BRB specimens: two having a single sinusoidal corrugated web and other two having double sinusoidal corrugated webs. It is shown that the FE model provides excellent correlations with experimental results.

Elastic buckling and load resistance of a single cross-arm pre-tensioned cable stayed buckling-restrained brace

This paper proposes a new type of buckling-restrained braces (BRB), namely a pre-tensioned cable stayed buckling-restrained brace (PCS-BRB) which is formed through introducing an additional structural system of pre-tensioned cables and a number of cross-arms to the outside of a common BRB. This new system significantly improves the BRB’s overall external restraining stiffness, hence increasing the load-carrying efficiency in its structural design. Due to its aesthetically appealing structure, it can be utilised in stadiums and so forth as a laterally resistant brace. Equilibrium method is utilised to deduce formulas of elastic buckling load of pin-ended PCS-BRB. The restraining ratio and the initial pre-tensioning force of cables are investigated to explore the effect on the axial compressive load-carrying capacity of the PCS-BRB through finite element analyses in elastic-plastic range. The findings indicate that two different types of buckling modes may occur in this PCS-BRB, namely single-wave symmetric and double-wave antisymmetric buckling modes. It was found from theoretical and numerical analyses that: a negative linear correlation exists between elastic buckling load and initial pre-tensioning force of the cables; the geometric parameters of the cable stayed system possessed remarkable effect on the elastic buckling load. In addition, the post-yield behaviour and ultimate compressive load-carrying capacity of the PCS-BRB is directly proportional to the restraining ratio, and there exists a lower limit of the restraining ratio which allows the inner core to reach full cross-sectional yielding without overall instability failure of the PCS-BRB. Furthermore, there exists an optimal initial pre-tensioning force of cables to make the load-carrying capacity of the PCS-BRB to reach a maximum value. The investigation of elastic buckling and load resistance of PCS-BRB provides fundamentals to further develop a complete design method of PCS-BRB.

Development of welded overlap core steel encased buckling-restrained braces

This paper reports development of a new type of buckling-restrained brace (BRB) named the welded overlap core steel encased BRB. A two phase experimental research program was undertaken where BRBs were investigated under subassemblage testing. The first phase of the program aimed at studying the performance of steel encased BRBs which utilize constant width core plates. Test results indicated that these braces develop unacceptably high compression and tension resistances and the behaviors of these BRBs under uniaxial testing and subassemblage testing are markedly different. In the second phase of the research program a new type of BRB which utilizes a welded overlap core was developed to improve the cyclic performance observed in the first phase. Experimental results showed that the braces sustain axial strains that vary between 2.0 and 2.5% and resistances in tension and compression were found to improve significantly when compared with the findings of the first phase. Welded overlap core steel encased BRBs were found to sustain cumulative axial strains that are 419 times the yield strain when properly detailed.

Finite Element Modelling and Analysis of “All-Steel” Dismountable Buckling Restrained Braces

This paper describes a theoretical investigation on the response of “all-steel” dismountable buckling restrained braces (BRBs) through the analysis of finite element models (FEMs). The focus of this investigation is on a special type of BRB developed for seismic upgrading of existing reinforced concrete buildings and experimentally tested previously. After a short summary of experimental results, the paper describes the finite element models and the analysis results. Subsequently, a discussion addresses the following issues: (i) influence of the core-to-casing clearance; (ii) influence of spacing of connections along the casing longitudinal axis; (iii) compression-to-tension strength ratio; (iv) core buckling wavelengths and core-to-casing interaction forces. Finally, the paper presents a comparison of numerical results and available analytical models.

Critical load and application of core-separated buckling-restrained braces

A new type of buckling-restrained braces (BRBs), called core-separated buckling-restrained braces (CSBRBs) is presented and investigated in this study. The CSBRBs are composed of two chord members and one or several continuous web plates that connect those members longitudinally. This core-separated section improves bending stiffness, thus resulting in lightness and convenience in fabrication and erection compared with conventional BRBs. The elastic buckling performance of CSBRBs is initially investigated because such performance depends directly on the restrain ratios, which should be specified in the design of all types of BRBs. The critical loads of pin-ended and fix-ended CSBRBs are then obtained based on the equilibrium method and verified by finite element (FE) elastic buckling analysis, respectively. Subsequently, the relationship between axial compression and core compressive strain of CSBRBs with different restrain ratios is studied by using FE elasto-plastic analysis. These research achievements provide the foundation for further investigations and applications for CSBRBs.

Experimental Study of the Steel Type Buckling Restrained Braces

In the domestic and international, experimental study for the Buckling Restrained Braces(BRBs) focuses on concrete type BRBs at present, but the type of BRB has a larger weight, and can change structure vibration characteristics, thus puts forward a new type BRB which is no longer filling in with concrete between kernel and outer components, meanwhile under monotonic loading and cycle repeated loading tests for the new BRBs, the experimental results show that the steel type BRB has good energy dissipation capacity, and can be applied to structure as passive control device.

Technical Note: Abrasive Waterjet Cutting Application

Abrasive waterjet cutting is a relatively little used technique for fabrication of structural steel components. The technique may permit economical fabrication of earthquake resistant structural steel members such as core elements of buckling-restrained braces. Abrasive waterjet cutting was used to fabricate yielding core elements for a new type of buckling-restrained brace. A 50,000 psi (344.7 MPa) waterjet and garnet abrasive cutting stream was computer numerically controlled to cut dog-bone and perforated yielding core configurations in 3/4 in. (19.05 mm) and 1-1/4 in. (31.75 mm) A36 steel bar stock. Abrasive waterjet cutting is a cold process and does not produce the heat affected zone associated with oxyfuel or plasma cutting. Tension coupon testing of a small number of samples of both traditionally machined and abrasive waterjet cut specimens indicated little change in the ultimate stress and only slightly reduced yield stress and total elongation for abrasive waterjet cut A36 steel coupons.

Component Testing, Seismic Evaluation and Characterization of Buckling-Restrained Braces

This paper reports on the results from a comprehensive component testing program on a type of buckling-restrained brace known as the Unbonded Brace™. The experimental data are used to: ~1! verify the results of theoretical predictions on the structural stability of the braces; ~2! validate the inelasitc capacity of the braces under severe earthquake demands; and ~3! calibrate a macroscopic hysteretic model that is found to predict, with fidelity, the brace force-displacement behavior. The study concludes that the unbonded brace is a reliable and practical alternative to conventional framing systems to enhance the earthquake resistance of new and existing structures; capable of providing both the rigidity needed to satisfy structural drift limits, while delivering a substantial and repeatable energy absorption capability.